The present invention relates to the allocation of a storage area to a virtual logical volume that conforms to Thin Provisioning.
Storage tier management technology that combines Thin Provisioning technology is known. In this storage tier management technology, the medium from which a real area (a substantive storage area) is allocated is selected using a virtual logical volume (hereinafter, a virtual volume) unit that conforms to Thin Provisioning. For example, according to Japanese Patent Application Laid-open No. 2007-66259, one or more media are associated beforehand with each virtual volume, and when there is a write to the virtual volume, a real area is allocated from any of the one or more media associated with this virtual volume.